In many recreation areas, a popular activity by water recreation enthusiasts is the operation of maneuverable water craft. These craft run the gamut from bumper boats, jet skis, ski boats, skiffs, and other water craft with more conventional designs. The objective of many of these recreational activities requires rapid acceleration and maneuverability of the craft. These craft must be extremely rugged because of the high stresses involved in operation, transport and handling.
Previous propeller driven water craft designs are generally either adaptations of standard ship hull designs with directionally fixed propellers and rudders primarily designed for forward motion, or circular designs with directionally movable propulsion means. The standard hull designs offers rapid acceleration and high speed capability but offers limited maneuverability due to the inability to propel full force in other than forward direction and increased hull resistance to translation. Circular craft offers excellent translation ability but are limited in turning, high speed or rapid acceleration ability due to the stress limitations of the moveable propulsion system and generally unstreamlined and central location of the propulsion system.
Placement and response of propulsion systems in either of the prior designs are constrained by motor transmission, shaft and propeller limitations. Direct drive motor/propeller combinations does not quickly respond to changes in controls due to large inertial forces. Speed control is also limited by minimum speed of the motor and nonlinear controls. Various transmission mechanisms provide additional placement flexibility and may aid speed control but add further weight and inertia, restricting response.
Multiple propeller adaptations of standard hull designs offer improved turning ability without the need for a rudder, but can not translate. Turning torque is also limited by the narrow ship width and response is limited by engine/transmission limitations.
Pilot operated control valves have previously offered fast response without the need for an additional power supply. However prior art designs were generally not compact and rugged, and required significant pilot fluid flow during normal operation conditions.